Autonomic Function in the Neonate: III. Methodological Considerations

Techniques are described that have been employed in interindividual and intraindividual comparisons of human infants in terms of autonomic nervous system function. With the use of cardiac-rate observations as a model, particular emphasis is given to the analysis of data that are patterned and involve time sequences. Newborn cardiac-rate responses to a short-duration standard stimulus follow a general pattern. From each trial one can derive magnitude estimates of the slopes, peak, and termination of the curve. The timing of each of these parametric estimates is also extracted from the trial curve. This technique avoids dependence upon averaging measures at arbitrary time intervals as is commonly done with such data. Sources of within-subject variability such as the effect of motor activity and the prestimulus cardiac rate (as it relates to response) are accounted for in the analytical procedures. The statistical models employed for the comparisons of individuals have been briefly described and will be dealt with more extensively in a subsequent report.9